private void Legend_Refreshed(object sender, ESRI.ArcGIS.Client.Toolkit.Legend.RefreshedEventArgs e)
{
if (e.LayerItem.LayerItems != null)
foreach (LayerItemViewModel layerItemVM in e.LayerItem.LayerItems)
if (layerItemVM.IsExpanded)
layerItemVM.IsExpanded = false;
}